Small intestine

Definition

The small intestine is a long, coiled tube that plays a crucial role in the digestive system, responsible for the majority of nutrient absorption. It connects the stomach to the large intestine and consists of three main sections: the duodenum, jejunum, and ileum. This organ is vital for breaking down food and absorbing essential nutrients and minerals into the bloodstream.

5 Must Know Facts For Your Next Test

1. The small intestine is about 20 feet long in adults, making it the longest part of the digestive system.
2. The surface area of the small intestine is increased by folds, villi, and microvilli, which helps maximize nutrient absorption.
3. Digestive enzymes and bile play critical roles in breaking down carbohydrates, proteins, and fats within the small intestine.
4. Most nutrients are absorbed in the jejunum, while vitamin B12 and bile salts are absorbed primarily in the ileum.
5. The small intestine has a specialized muscular layer that enables peristalsis, ensuring that food is moved efficiently through its length.

Review Questions

• How does the structure of the small intestine facilitate its role in nutrient absorption?
  • The structure of the small intestine is highly specialized to enhance nutrient absorption. The inner lining contains numerous folds and projections called villi and microvilli, which increase its surface area dramatically. This expanded surface area allows for more efficient contact between digested food and absorptive cells, optimizing the uptake of nutrients into the bloodstream.
• Discuss the roles of bile and digestive enzymes in the functioning of the small intestine.
  • Bile and digestive enzymes are crucial for effective digestion in the small intestine. Bile, produced by the liver and stored in the gallbladder, emulsifies fats to enhance their breakdown. Digestive enzymes from the pancreas further break down carbohydrates, proteins, and fats into simpler molecules that can be absorbed by the intestinal walls. Together, they ensure that nutrients are adequately prepared for absorption.
• Evaluate how disruptions in small intestine function can impact overall health.
  • Disruptions in small intestine function can have significant health implications. Conditions such as celiac disease, Crohn's disease, or infections can impair nutrient absorption, leading to malnutrition and deficiencies in essential vitamins and minerals. This malabsorption can cause various symptoms like weight loss, fatigue, and gastrointestinal discomfort, affecting overall well-being and quality of life.

Related terms

Duodenum:

The first section of the small intestine where most chemical digestion occurs, receiving bile from the liver and digestive enzymes from the pancreas.

Villi: Tiny, finger-like projections lining the walls of the small intestine that increase surface area for absorption of nutrients.

Peristalsis:

The rhythmic contraction of muscles in the digestive tract that propels food through the intestines, including the small intestine.